Goals for the coming year: 1. We shall survey a wide variety of tissues for levels of FBP-CII under different conditions of nutrition. We will attempt to determine how much of the available binding capacity is saturated under these different conditions. 2. We will extend our studies on the FBP of rat liver mitochondria to mitochondria of other tissues to learn: a) whether all mitochondria have a similar binding protein and b) whether we can obtain a species that can be made sufficiently deficient in folate so that the mitochondrial function is impaired. Other studies will be carried out to investigate the possiblity that this protein acts in electron transport with the bound tetrahydropteroylglutamate ligand undergoing reversible oxidation reduction.